Kaizen! Post-migration cleanup

In our 6th Kaizen, we talk with Jerod about all the things that we cleaned up after migrating changelog.com from a managed Kubernetes to Fly.io. We deleted the K8s cluster and moved wildcard cert management to Fastly & all our vanity domain certs to Fly.io. We migrated the Docker Engine that our GitHub Actions is using - PR #416 has all the details. We did a few other things in preparation for our secrets plan. Thank you Maikel Vlasman, James Harr, Adrian Mester, Omri Gabay & Owen Valentine for kicking it off in our Slack #shipit channel. Gerhard's favourite improvement: the new shipit.show domain.